Front Weights

[stewart]

Hi all,

My car is about to head to the suspension shop for final adjustments prior to hopefully having its braking and lane change testing done this thursday. If it passes not many more specific jobs to do to pass registration (he says optimistically knowing that the bumper bars he has to fit are not yet done...don't ask!).

Anyway, having now done a total of 16 km illegally around home I find that at 80kph the front end is just a little (lot) lighter than I feel comfortable with. I want to fit some weight in the front end anyway and remember having seen some comments by people about having added weight, but how much is the general consensus?.

I hope to weigh the car tomorrow which will help give an idea as final suspension settings should really be done with the weight in place. Any extra advice is always welcome though.

So, anyone care to advise how much, if any, extra weight they place in the front of their cars to assist handling? I do have a front undertray which mounts under the radiator and then under the floor which hopefully will assist air flow and handling too.

Thanks

[chris.richard]

An off the wall, guess of 25kg increments? Based on the idea that it's going to be something of the order of magnitude of a human body to make a difference. The further forward the better from the point of view of maximum downforce per kilo, but the further forward, the more it'll increase the rotational inertia for cornering.

[rutthenut]

I hadn't heard of anyone specifically adding ballast to the front of the car, although I can see that would work - it's just not an approach I would like to use.

If you've got a spare wheel up front, that will help.

What will help more is if you can move some weight from the rear of the car to the front. About the only real candidate for that is the battery, which at least is a heavy component. To do so, you will need to make up a new battery tray of some sort, which may also require changes to the spare wheel mounting. It can be done if you have a space-saver tyre though.

If you fit a plumbed-in extinguisher, that can also go in the front and help a little with the weight balance.

Maybe the feeling of a light front end isn't just the lack of actual weight - you may find that changes to tyre pressures and suspension alignment (especially caster) will help.

A further option can be to add a small chin spoiler, which is claimed to help the front stay down a bit better.

I've not felt the need for this, but others have done so and claim improvements. Unfortunately this can cause problems with ground clearance, so the need to run the front end of the car higher can negate any of the benefits when in use on the road.


I suppose that you could just add some ballast to see if that gives you the desired improvement. If it doesn't, then you can take it out again without needing to make other changes to the car.

Cheers

[Stratos]

Personally, I would move as much weight from the rear to the front as is possible to get a better weight balance, and more pressure on the front tyres. The Alfa V6 is a heavy lump to have at the back, and anything you can do to redistribute the weight is going to help to a smaller or larger degree.

A Red Top 25 battery is very small, but easily sufficient for a Stratos, and can be fitted into a small gap at the front. That's what I fitted into the front of my car.

I've now got my petrol tank at the front, but that would exclude the possibility of carrying a spare wheel, and it's quite small capacity.

There's only so much you can do as there aren't all that many items that can be relocated.

[David May]

The mere idea of adding weight goes against all Stratos prniciples. If you want a heavy car, why start with a Stratos!

I personally enjoy not having to have power-steering and being able to feel the road, and I would only call mine light above 250kmh (which I have won't be trying to achieve again!)

It's easy to dial-in some more castor if all you want is heavier steering or fit a high-ratio rack!

Dave May

[Sando]

Hi Stewart
Hope it all goes well for you with the tests.

As per the other replies shifting weight from the back to the front as much and as low as poss is where I think is the way to go. (Probably to the extent of having to do away with a spare though, but to me that's additional weight not moved weight!) I've gone for Battery and soon Extinguisher up front instead of a spare wheel.

One other thought that hasn't been aired is that of the ride height / angle of attack if you know what I mean. I'm not a handling expert by any means, but I've always wondered about the effect of the downforce from the rear spoiler at high speed actually making the rear lower and therefore creating lift at the front by sitting down at the back? if you get my drift. This would probably make a big difference with such a flat bottomed car. (The Chequerd Flag car always looked very high at the back to me?)
I'm sure ride height would also come into play along with the correct castor / toe settings.

And not having driven mine yet (still!) I also wonder what effect the lamp pod has on all this too?? Certainly extra weight up front but also upsets the aerodynamics at high speed I would think?

let us know how you get on and any improvements you find.
cheers
Rob:cool:

[stewart]

Thanks guys,

The consensus certainly seems to be not to add weight, except for needed accessories!.

As I say, I have seen some comments, somewhere, about extra weight being added, but I didn't remember the cars I have been in having weight added.

I don't know how much castor has been dialled in yet but will after today. I am just trying to cover eventualities, remembering that after all, I have only done 16km, 80kph max and the only adjustments have been to tyre pressures which seems to have made no difference.

My front tyres are 40 profile which should help make the steering light. I think the rack may be a little tight as the steering feels heavier than I think it should and the self centring is very poor. It's not the heaviness of the steering that is the problem it is the floaty feeling. Maybe I just have so much power I'm doing wheel stands....:D

My battery is in the engine bay down low behind the passenger and I'm not going to move it. Spare tyre isn't in yet as I am having to make a new removable mounting bracket but that will help. No plumbed in fire extinguisher either. A front spoiler is definitely on the to do list but let's just get the damn thing on the road! My engine is the Nissan which shouldn't weight any more than the Alfa I'm sure.

If David can go 250kph and only then get worried about lightness and John can win on the racetrack without added weight and adding it isn't common then I will keep looking and playing a bit longer before taking that route!

I'll post my steering etc specifications in the next couple of days for interest.

cheers,

[chris.richard]

"Some people" might have added weight in the drivers seat area, and not be admitting it!:eek:

[Stratos]

There was an article in CCC several years ago comparing several replicas, and I'm sure it mentioned that one of them had a steel plate bolted under the front to give more weight at the front.

I think only one of the cars tested had this.

Steering geometry adjustments, and relocation of various items, should get you to a good handling car without needing to resort to ADDING weight to the car.

[chris.richard]

Really, the only good reason to add weight is to meet some minimum weight requirement for competition.

[stewart]

Hi all,

Some information for you all to compare and ponder over.

I had the car down having suspension and steering examined today and learned the following:

1) The steering was binding because the bracket under the dash was too tight. I thought I had checked that this wasn't happening...obviously not well enough. Anyway it is now loosened off and she self centres beautifully.

2) Car weighs in at 960 kg with a weight distribution of 39.6% front and 60.4% rear. With spare wheel in place make this 40.6% and 59.4%. This compares pretty much with Dave and Jan's cars as tested in CCC in Sept '02. There was no spare wheel or pax seat in car so add 15kg but there was about 25L of fuel so take off 20kg. Let's say dry weight of about 950kg.

3) With brake bias fully set to rear I can still lock the front wheels if I stand on the brakes. I have pretty big front brakes though. I am not worried about it passing the braking test this week.

4) Interesting but probably not surprising to note that my seat is right in the middle of the car and with me seated in it there is no change in front/rear weight distribution.

So, Dave, there was an article in CCC in may 1995 that included a car (Beta powered) with 45lb of weight in the spare wheel. That was where I got the idea. I think I will stay off that idea for the time being. Like everyone else I am loathe to add unneccessary weight.

All in all a good day except for the new scratch in the paintwork on the body, not surprisingly no-one is admitting to that one!

No camber/toe etc figures yet, but I will provide them when I get them.

Thanks for the help,

Ciao

[vojx]

re - 4) Interesting but probably not surprising to note that my seat is right in the middle of the car and with me seated in it there is no change in front/rear weight distribution.


. . . So where's the gear change?:p

[stewart]

Oh how easy it is to leave oneself open.....:D

[stewart]

Just to continue this little story.

Passed braking and emissions testing today. Brakes a little wobbly though as rears hardly working and fronts easy to lock. Had to balance trying to stop within the distance (from 60 and 100kph) and not lock up brakes. Have now clocked up a magnificent total of 34km and reached a top speed of 135kph...starting to feel like it is a real car at last.:cool:

My brakes are Subaru front and Nissan 300ZX rear calipers with 280mm vented rotors front and rear. Only running Fiat 131 booster and master cylinder though. We will measure fluid pressure at each rotor but expect that not much going to the rear and heaps to the front so will almost certainly have to increase master cylinder bore and maybe fit bias to front rather than rear.

Any other suggestions from welcome.

Still it has passed and I can progress onto the next items on the list. Not long now before another replica, very long term build, finally makes it onto the road...stay tuned.

ciao

[chris.richard]

Congratulations -it sounds fun! Envy, envy!:cool: One day.....